Method of treating fluidized particles while conveyed



Jan. 19, 1965 'J. M. MORRIS 3,166,383

METHOD OF TREATING FLUIDIZED PARTICLES WHILE CONVEYED Original FiledDec. 19, 1956 2 Sheets-Sheet l Q g Q Q INVENTOR.

JOHN M MO/iR/S 8 BY Jan. 19, 1965 .1. M. MORRIS 3,166,333

' METHOD OF TREATING FLUIDIZED PARTICLES WHILE CONVEYED Original FiledDec. 19. 1956 2 Sheets-Sheet 2 INVENTOR.

Zii.g 17' JOHN M MORE/5 ATTORAEYS ETHOD or TREATING FLUIDIZEE) PARTICLESWHELE CONVEYED John Morris, Louisville, Ky., assignor, by mesne assign-It often is desirable to heat or cool powders for the purpose ofpromoting or retarding polymerization or other 'chemical reactions orfor driving off adsorbed gases or moisture or otherwise conditioning thepowders for further processing or for storage or use.

It is well known that because of the nonheat-conducting properties ofmasses of pulverulent material, the operation of chan ing thetemperature of such masses is'time consuming, and the uniformdistribution of a higher or lower temperature through such masses oftenjrequires prolonged heat soaking or chilling.

This invention relates to a. method and apparatus for not only rapidlyand uniformly transferring heat to or from pulverulent material but alsoconveying such material from one point to another while theheat-transfer is occurring, whereby pulverulent material -of any averagetemperature can be continuously received at one point in the apparatusand rapidly heated or cooled while being United States P t O conveyed toanother point where it .may be discharged with a higher or lowertemperature uniformly distributed .throughoutthemass.

Finely powdered commodities such as flour, starch, Portland cement,molding powders, pigments and the like cannot be moved in large volumesalong a vibratory conveyor which functions'by tossing particles upwardlyand forwardly, for the reason that particles of fine powder in 3,166,383Patented Jan. 19, 196.5

whereby fiuidizable pulverulent materials, or materials which contain asubstantial proportion of particles-which if segregated could befluidized, are moved rapidly and economically from place to .place whilebeing rapidly and uniformly heated or cooled.

And it is still a further object of this invention to provide a methodand apparatus wherein aeration, vibratory conveying and heat transfermutually cooperate in processing of pulverulentmaterials.

Other objects and advantages of the invention will appear upon perusalof the following description, as illustrated by the accompanyingdrawings in which: 7

FIG. I is a side elevational view of apparatus embodying one form of theinstant invention;

FIGJI is a transverse cross sectional view on a somewhat enlarged scaletaken substantially as indicated by the line II-II of FIG. I;

FIG. III is a fragmentary perspective view showing a modified form ofthe instant invention; and

FIG. IV is a transverse crosssectional view similar to 'FIG. II butshowing a further modified form of the in 'ventioh.

This description and the accompanying drawings are intended to describeand illustrate a preferred form of the instant invention but nottoimpose limitations upon its scope.

Referring now more particularly to the drawings, and

first to FIGS. I'and ll thereof, the apparatus comprises'a base 1 in aninclined path of vibration indicated by the it and restoring to theparticles individual freedom of movement. a

-If a mass of powder is aerated to such an extent that it is fluidized,the insulating properties of the mass are greatly reduced and thediscreet particles can be readily heated or chilled. Heat canjbetransferred toor from the discreet particles of a fluidized powder byradiation or conduction. Such heat transfer also is promoted byagitation of particles such asoccurs when theyare tossed along avibratory conveyor.

It is an object of this invention to provide means ,whereby pulverulentmaterials can be heated or cooled arrow 4, The conveyor assembly 5 issupported on and 7 connected to the tops of said series of resilientmembers 2.

The resilient members 2 as herein shown are to be regarded as merelyillustrative. Numerous other forms thereof, e.g. those that aredisclosed in Robert M. Carrier,

Jr., United States Patent No. 2,706,112, granted April 12,

i 1955, may be substituted. Moreover, in some instances,

In the preferred method of operation, at least one-half of the materialby weight is in a completely fluidized state. -Under those conditions,the conveyor assembly 5 preferably is inclined. slightly so that thefluidized material will flow downhill, the angle of inclination beingadjusted to give maximum efficiency. If desired, the conveyor assemblymay be helical, as disclosed in Robert M. Carrier, Jr., United StatesReissue Patent No. 22,904,

It is a further object to provide a method and apparatus for heatingmixtures of fluidizable fine powders and coarser granules.

path 4.

It is a further object to provide a method and apparatus granted August12,1947. V v

The. conveyor assembly 5 comprises mating opposed channel-shaped parts 6and 7 which are bolted or otherwise secured together to clamp a porousor semi-per- .me'able deck .8 therebetween.

If desired, struts may be secured at longitudinally spacc'dintervalstransversely across the upper edges of the lower channel-shaped part 6to rigidify the deck ,8

and also to 'assistin supporting the loads of conveyed material thereon.M

Any suitable means may be employed for imparting to the conveyorassembly vibratory movement along the The vibratory movement-impartingmeans is shown, by way of example, as comprising 'an electricOthervibratory movement imparting means such as electromagneticvibrators, revolving eccentric weights or the like are well known in theart and may be substituted for the crank and connecting rod vibratorymovement imparting means." r

Above one end of the conveyor assembly is a feed hopper 14 forintroducing conveyable material upon one "end of thedeck 8. Connected tothe lower channelshaped part 6 adjacent the feed hopper end of the conveyor assembly 5 is a flexible hose 15 which leads into a chamber formedbetween the lower channel-shaped part 6 and the deck 8. Thesaid flexiblehose15 communicates at its other end with aunit 16 for supplying a gassuch as air under pressure, which may include an air preheater 5 orcooler, aswell as a motor-driven blower" and volume and pressurecontrols, all of which are commercially available and none of which areshown in the drawings, Although the gas to be supplied under pressurethrough the tube 15 will in most cases be air, other gases may bef-employed. When the terms ai-r? and aeriform fluid are used in thisspecification, those terms are intended to mean any suitable aeriformfluid. i As above indicated, the air may be preheated so that it mayserve to drive off adsorbed gases or moisture or to promotepolymerization or otherwise condition the powf der, as well as to aerateor fluidize it. Similarly, the air may be chilled to extract heat fromthe powder or other- "wise condition it.

r The form of apparatus shown in FIGS. I and II confines the heated orchilled air within the conveyor as- "sembly 5 until the air reaches adischarge port 17, from whence the air if desired may berecirculated.Instead of, or in addition to, preheating or cooling the air before itis supplied to the conveyor assembly 5, heat transfer tubes 18 havingfins 20 may be located within the upper channel-like part 7 of theconveyor assembly.. Heating or cooling tubes 19a as shown in FIG. III,may

be employed instead of or in addition to the tubes 18. The tubes may becarried by the vibratory trough assembly 5 as shown in FIG. II, or theymaybe stationary as ;indicated in FIG. III. 'Where heat transfer tubesare 'employed the particles of powder as they dance along "the deck 8are heated, or cooled, largely by radiation from the tubes or from theparticles. In such case it' is less important to recirculate the air,and the top of the con- "veyor assembly 5a may be left uncovered in themanner .shown in FIG. III, particularly when the apparatus is designedfor cooling. 'The resilient supporting membersZa, the plates 3a, 'thelower channel-shaped part 6a and the deck 8a or the modification shownin FIG. III are similar to the cor- I responding elements shown in FIGS.I and II. i In the form illustrated by FIG. IV the tubes 1% lie beneaththe deck 8b. This arrangement is most eficacious when the deck 81) is ofperforated metal and functions as a heat transfer element when it isheated or cooled by the tubes 1%. The tubes in any modification can bestationary orthey can vibrate with the conveyor assembly.

"It'has been possible heretofore to heat powders consisting entirely offine particles by aerating such pow ders to aistate of completefluidization and then, by means of'pumps, jets, siphons or the like,forcing themto flow 1 over heating coils. The necessity for pumps, jetsor "siphons'is obviated by the present invention, in which the vibratoryconveyor not only agitates the stream of they flow along together.

granules or even lumps, which mixtures could not be handled by pumps,jets or siphons.

. A vibratory conveyor will not convey a completely fluidized powderuphill, but a completely fluidized powder will flow downhill along avibratory conveyor. The rate at which a completely fluidized powder willflow along a conveyor depends principally upon the degree of downwardslope, though the rate of flow may be somewhat modified by vibratorymovement. Coarse granules which cannot be fluidized will not flow freelyalong a moderately sloping conveyor, but can be conveyed therealong byvibratory movement. By adjusting the slope of the conveyor to convey'thefluidized part of an aerated mixture of fine powderand ,coarse granules,at a desired speed and adjusting the vibratory movement of the conveyorto convey the non-fluidized part of the mixture at a desired speed, bothparts can be heated or cooled as Indeed, it is possible to make theparts of the mixture move at different speeds and thus subject each ofthem to heat transfer treatment for a different period 'of time, tobring each different part to a desired temperature. Thus, where thepulverulent 'rnaterial contains fine fluidizable particles and coarserparticles which are non-fluidizable or less readily fluidizable, thevolume of air passed through the gas-permeable deck 8 may be socontrolled that the fine particles are separated from the coarserparticles and fluidized and caused to flow along the conveyor bygravity, while the coarser particles are not fluidized and are caused toform a layer on the deck surface and to be moved thereperiod of time toenablethem to absorb or give up a 'greateramount of heat, as the casemay be.

While the new combination of cooperating aerator,

vibratory conveyor and; heat transfer elements function mostsatisfactorily in many situations if the line powder being processed isaerated to complete fluidization, the new combination functionssatisfactorily in other situf at-ions even if the fine powder is notcompletely fluidized.

Broadly stated, this invention provides conveying and temperaturechanging apparatus for pulverulent material comprising an elongatedgas-pervious deck, said deck having a permeability such that there willbe substantially no sifting therethrough'of the finer particles of the'material to be conveyed while providing for the passage therethrough ofaeriform fluid, means for causing the flow 501 upwardly through saiddeck of aeriform fluid at a rate not substantially in excess of thatrequired to fluidize 'the bed of material to be conveyed, and means forvibrating said deck'with a motion such that the work surfaceacceleration due to gravity.

There are certain important factors to be observed in fth'e design,construction and operation of the apparatus of this invention. They are:

v(l) The nature of the materials to be processed,

(2) The initial'and final temperature of the material, (3') The degreeof aeration of the material,

-(4) The nature of the permeable deck of the conveyor,

and

I (5 The nature of the vibratory motion of the conveyor deck.

When" the term fluidize is used in this description and in the claims,it is intendedto refer to a' condition in which aeriform fluid passesupwardlythrough a mass 7 mass assume limited motion without beingentrained in lmaterial for more eific'ient heat transfer but also conveys it over such heat transfer units as are employed.

Moreover, it conveys mixtures .of fine powder and coarse the fluid; asdistinguished frorn conditions' wherein the particles havea velocitywhich approaches that of the air stream and thus may become entrained'insuch stream.

' syr'rnn'pEonen oE AERATToN on THE 3 (1) THE NATURE OF THE MATERIAL TOBE V PROCESSED g It is necessary only that the material to' be conveyedand heated or cooled contain a substantial proportion ofparticles which,when segregated and'arranged in a bed as, for example, 4" thick, can befluidized by aeration from beneath. Thus the material may consistentirely of such particles or it may contain only a substantialproportion of such particles.

When a nonaerated admixture of fine particles and heavier and largerparticles is subjected to the action of a vibratory conveyor, thetendency is for the material to stratify with the finer particles in thelower layer adjacent the conveyor deck; and to the extent that suchstratification occurs, it interferes with the heat ransfer and withefiicient operation ofthe vibratoryconveyor.

When the deck of the vibratory conveyor is made permeable and a uniformblanket of air is caused to flow upwardly therethrough, then the orderofstratification is reversed, depending upon the nature and quantity ofthe fine material and the degree of aeration. Any substantial amount ofaeration, however, will thus reverse p the Stratification and carry theline material to the upper portion of the layer so that the largernon-fluidizable heavier particles are in contact with the permeable deck1 of the vibratory conveyor, and they are moved along by an action whichis apparently similar to that which occurs when such heaviernon-fiuidizable, material is by itself conveyed on ayibratory conveyorhaving an impermeable deck. The ratio of surface area to mass of thelarger particles is much less than the ratio of area to mass of the fineparticles However, such heat as is absorbed at the surface of a largerparticle is readily diffused throughout the particle by conduction.

When the material to be conveyed consists of 'a mixture of coarsegranules with particles which can befiuidized, the use of a vibratoryconveyor with -a permeable deck, whereby thematerial thereon maybeaerated, makes possible conveyance and heat treatment of such material.

which cannot be conveyed or heat treated-effectively by use of either avibratory conveyor by itself or a slide conveyor which relies entirelyon aeration.

2 THE INITIAL AND FINAL TEMPERATURES OF THE MATEREAL The material insomecases may enter theapparatus at room temperature, g; 7080 F., andbeheated for the purpose of promoting"polymerization or other chemicalchangeto any desired degree below thepoint where decompositionor'charring occurs. The optimum final desired. i' ln othercasesythefmaterial may be received temperature will vary withthe-material and the result in'g compositions and adhesives arerequiredto, bestored Such ma- MATERIAL Generally, injthe practiceof'this invention, a lesser volume of 'air' is required, to fiuidize'the agitated material than in those cases where agitation is notemployed; The" degree of aeration should be insuflicient to entrain theparticlesfbut at least sufficient to loosen the mass? Vlhen ail mixtureof material is conveyed which conaims a substantial proportion ofmaterial which is not fluidizable, the degree of aeration may bejthatwhich would be required'tok fluidize that portionof the mass amass? 1(4) THE NATURE OF THE PERMEABLE DECK OF THE CONVEYOR The primaryrequisite of the permeable deck is that' it be capable of transmittingupwardly therethrough a substantially uniform blanket of air, inrelatively low volume per unit of area, without permitting the siftingdownwardly through the deckiof .any substantial proportion of the finesof the material. Stated in another way, the deck must not permit thesifting therethrough of any substantial proportion of the work but mustbe capable of transmitting a uniform blanket of air which breaks thevacuum between the body of material to be treated and the upper surfaceof the deck and counterbalances the atmospheric pressure upon the uppersurface of the material.

The deck may be made of a wide variety of materials.

Closely woven fabrics such as those used in conveyors torily, providedthat they have the desired permeability and are able to withstand thetemperature of the material being conveyed. When higher temperatures areencountered, inorganic materials are, of course, preferred; Thus, thedeck may be formed of porous stone slabs or metal plates or screenshaving a mesh oropening size such as to provide a permeability factorwithin the ranges given above.

.When the deck consists of a metal screen, an electrical current can bepassed through the screen so that the screen serves as a heatingelement.

When a foraminous plate or screen is used, the individual openings mustbe sutficiently small so that there will be no local areas of intensevelocity which would cause geysering of the material on the deck.

When reference is made to the maintenance of a uniform supply ofaerating fluid, bythis is meant the maintenance of that condition in anylocal area of the deck,.

although it should be noted that the volume and velocity of the supplymay be different in different longitudinal or transverse areas of thedeck.

(5 THE NATURE on THE VIBRATORY MOTION be varied over rather wide limits,provided, however, that 'the relationof the frequency to the amplitudeof the .i -stroke is such that anincremental area of the active surface.of the deck has a vertical acceleration which is at lea'stequal to andpreferably greater than the acceleration of gravity. For practicalpurposes, whenhandling mostxmaterials, the vertical acceleration ofanincremental area of the deck should lie within the'range of from 1.5.

to times the acceleration of'gravityi The thickness of the layer to bemaintained on the permeable deck for maximum efiiciency depends on avariety ot factors, mostly. related to the characteristics of thematerial to be conveyed and, of course, the de- {gree of slope of the"deck. Ordinarily, for most ma terials,"a layer thickness of more than1'. and preferably about 4" will give satisfactory results. The layerthickness canj be regulated ina vibratory conveying apparatus byregulating theirate of feed" thereto, and in a. feeder type of apparatusthe layer thickness can be regulated y Varying the distance between thedeck and the opening of the hopper. f

"In many cases, all other conditionsbeing the same,

.the' speed at which the layer of material is conveyedincreases, withinlimits, with an increase in the thickness ofthelayer.

areasss a .The adjustment in layer thickness for maximum speed ofoperation can be made readily for each installation when handling aspecific type of material by merely observing that thickness which willgive maximum velocity of movement forwardly on the conveying deck. Theadjustment of the layer thickness should be coordinated with anadjustment of the volume of air caused to move upwardly through thepermeable deck and with an adjustment of the rate of heating or cooling.These three factors are so. interrelated that it is impossible to give auniversally applicable formula. Moreover, the varying characteristics ofthe different material would require various formulae for variousmaterials.

The 'following are specific examples of this invention:

Example 1 'per cu. ft., at a rate of more than 15 tons per hour;

Air admitted at'a temperature of 200 F., supplemented by heating bymeans of the tubes 18, will reduce the moisture content of the'fluorspar from 9% to.3%. The conveying deck was substantiallyhorizontal.

' Example 2 w A conveyor like that'used in Example 1 but having an 8"Wide deck, vibrated at stroke and a frequency or 480 cycles per minute,conveyed Portland cement dust of 250 mesh at a rate of about 45 ft. perminute,

equal to about 15 tons per hour, the tendency of the dust to absorbmoisture being counteracted by preheating the air supplied through theporous deck.

Example 3 A conveyor like that used in Example 1, vibrated at 'a strokeof A1" and 'a frequency of 825 cycles per minute, conveyed phosphatefertilizer dust of -250 mesh at a greater rate than the cement dust wasconveyed in Example 2. r

In all of the foregoing examples, the porous deck was a canvas membranehaving a pressure drop of about 1.5 lbs. per square inch when passingair at the rate of 10 cu. ft. per minute per square foot, and an airflow just sufficient to fluidize the material, ranging up to about -10cu. ft. per minute per square foot was used. I

The apparatus'of this invention has been used suc cessfully inprocessing a synthetic detergent under such atmospheric conditions thatthe material partially age:

glomerated, which would have, made it impossible to process the materialon a conveyor relying entirely on aeration.

. "This is a continuation of'my copending application Serial No.629,380, filed December 19, 1956, now abandoned, which. is'acontinuation-impart of application 'Serial No. 547,073, filed November16, 1955, entitled Method and Apparatus for ConveyingPulverulent'Malterial, which has matured into Patent No. 2,795,318.

The invention described above is subject to modification within closed.

the spirit and scope of the invention-as dis:

Having described theinventioml claim: 1 V

of thematerial in a gas-fiuidizedphase above the deck bypassing a gasupwardly through the material. at a rate I sufiicient to fiuidizeonlypart of the material and insuffioient to produce substantialentrainmentof such material,

i(b).causing said gas-fluidized phase ,to flow along the deck, (c)conveying theremainder of the material along the deck by vibrating thedeck in a controlled path of motion having a substantial verticalcomponent and a substantial horizontal component, (0!) subjecting thematerial to heat exchange, said material containing a substantialproportion of relatively coarse particles, and (e) regulating therelative rates of flow of the gas fluidized phase and the vibratorilyconveyed material such that the fluidized phase and the coarserparticles reach a discharge point on the deck at the same time they haveattained a predetermined temperature.

2. A method of changing the temperature of material containing asubstantial proportion of fiuidizable fine particles, while conveyingthe material along a conveyor deck, comprising the steps of (a)maintainingonly part of the material in, a gasrfluidized phase above thedeck by passing a gas upwardly through the material at a rate sufiicientto iiuidize only part of the material and insufiicient to producesubstantial entrainment of such material, (b) causing said gas-fluidizedphase to flow along the deck, (0) conveying the remainder of thematerial along the deck by vibrating the deck in a controlled path ofmotion having a substantial vertical component and a substantialhorizontal component, and (d) subjecting the material to heat exchange.

3'. A method of changing the temperature of material containing asubstantial proportion of fluidizable fine particles, while conveyingthe material along a conveyor deck, comprising the steps of (a)maintaining only part of the material in a gas-fluidized phase above thedeck by passing a gas upwardly through the material at a rate sufficientto fiuidize only part ofthe material and insuflicient to producesubstantial entrainment of such material; (b) causing said gas-fluidizedphase to flow along the deck; (0) conveying the remainder of thematerial along the deck by vibrating the deckin a controlled path of'motion having substantial vertical and horizontal components; and (d)subjecting the material to heat exchange, said fiuidizablematerial beingin contact with a heat exchange surface; p

4. A method of changing the temperature of material containing asubstantial proportion of fluidizable fine particles, while conveyingthe'material along a conveyor deck, comprising the steps of (a)maintaining only part of the material in a'gas-fluidized phase above thedeck by passing a gas upwardly through the material at a rate sufii-'cient to fiuidize only partof the material and insufiicient to producesubstantial entrainment of such material, (12) causing saidgas-fluidized phase to how along the deck,

(6) conveying the remainder of the material along the deck by vibratingthe deck in "a controlled path of motion hav ng substantial vertical andhorizontal components,

I d) subjectingthe material to heat, exchange, said materialcontaini'nga substantialproportion of relatively coarse particles, and(e) -regulating the-relative rates of fiow of the gas-fiuidizedphase andthe vibratorily conveyed mat'e r'ial'tc control the relative rates ofheat ex- ,change, said fluidizable materialbeing in'contact with a heatexchange surface.

References Cited in the of this patent UNITED STATES PATENTS? 693,455Stanl y-;; ;1 Feb. 18; 1902 1,068,162 Payne "Ju1 22, 1913 2,014,249Fletcher: Sept. .10, 1935- 2,094,786 Flint Qct. 5,1937 2,353,293 Kendallet a1. sea. '12, 1944 2,629,938 .Montgomery ..';1. Mar. 3,19532,795,313. Morris June- 11,1957 2,876,557 Ducatteauj Mar. 10, 1959 rFOREIGN PATENTS Great Britain Ma-r. 2,1955

1. A METHOD OF CHANGING THE TEMPERATURE OF MATERIAL CONTAINING ASUBSTANTIAL PROPORTION OF FLUIDIZABLE FINE PARTICLES, WHILE CONVEYINGTHE MATERIAL ALONG A CONVEYOR DECK, COMPRISING THE STEPS OF (A)MAINTAINING ONLY PART OF THE MATERIAL IN A GAS-FLUIDIZED PHASE ABOVE THEDECK BY PASSING A GAS UPWARDLY THROUGH THE MATERIAL AT A RATE SUFFICIENTTO FLUIDIZE ONLY PART OF THE MATERIAL AND INSUFFICIENT TO PRODUCESUBSTANTIAL ENTRAINMENT OF SUCH MATERIAL, (B) CAUSING SAID GAS-FLUIDIZEDPHASE TO FLOW ALONG THE DECK, (C) CONVEYING THE REMAINDER OF THEMATERIAL ALONG THE DECK BY VIBRATING THE DECK IN A CONTROLLED PATH OFMOTION HAVING A SUBSTANTIAL VERTICAL COMPONENT AND A